0000844779bf:S000038448Member2012-06-012013-05-3100008447792012-06-012013-05-310000844779bf:S000038448Memberbf:C000118599Member2012-06-012013-05-310000844779bf:S000038448Memberbf:C000118600Member2012-06-012013-05-310000844779bf:S000038448Memberbf:C000118601Member2012-06-012013-05-31pureiso4217:USD<div style="display:none">~ http://www.blackrock.com/role/ScheduleShareholderFeesBlackRockRealEstateSecuritiesFund column period compact * ~</div><div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualFundOperatingExpensesBlackRockRealEstateSecuritiesFund column period compact * ~</div><div style="display:none">~ http://www.blackrock.com/role/ScheduleExpenseExampleTransposedBlackRockRealEstateSecuritiesFund column period compact * ~</div>2013-05-31BLACKROCK FUNDS485BPOS00008447792013-05-312013-05-31false2013-01-31Fund Overview<b>Investment Objective</b><b>Fees and Expenses of the Fund</b><b>Shareholder Fees<br/>(fees paid directly from your investment)</b><b>Annual Fund Operating Expenses<br/>(expenses that you pay each year as a<br/>percentage of the value of your investment)</b><b>Example:</b><b>Portfolio Turnover:</b><b>Principal Investment Strategies of the Fund</b><b>Principal Risks of Investing in the Fund</b><b>Performance Information</b>The investment objective of BlackRock Real Estate Securities Fund (the &#8220;Fund&#8221;), a series of BlackRock Funds<sup>SM</sup> (the &#8220;Trust&#8221;), is to seek total return comprised of long-term growth of capital and dividend income.This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in the fund complex advised by BlackRock Advisors, LLC (&#8220;BlackRock&#8221;) and its affiliates. More information about these and other discounts is available from your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock, The PNC Financial Services Group, Inc. and their respective affiliates) (each a &#8220;Financial Intermediary&#8221;) and in the &#8220;Details About the Share Classes&#8221; section on page 14 of the Fund&#8217;s prospectus and in the &#8220;Purchase of Shares&#8221; section on page II-58 of Part II of the Fund&#8217;s Statement of Additional Information.This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund&#8217;s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:The Fund pays transaction costs, such as commissions, when it buys and sells securities (or &#8220;turns over&#8221; its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund&#8217;s performance. During the period from September 28, 2012 (commencement of operations) to January 31, 2013, the Fund&#8217;s portfolio turnover rate was 25% of the average value of its portfolio.Under normal conditions, the Fund invests at least 80% of its net assets plus any borrowings for investment purposes (measured at the time of purchase) in a portfolio of equity investments in issuers that are primarily engaged in or related to the real estate industry inside the United States. An issuer is primarily engaged in or related to the real estate industry if it derives at least 50% of its gross revenues or net profits from the ownership, development, construction, financing, management or sale of commercial, industrial or residential real estate or interests therein or has 50% of its assets in real estate or real estate interests. The Fund may invest up to 20% of its net assets plus any borrowings for investment purposes (measured at the time of purchase) in a portfolio of equity investments in issuers that are primarily engaged in or related to the real estate industry outside the United States and fixed-income investments, such as government, corporate and bank debt obligations.<br/><br/>Real estate industry companies may include real estate investment trusts ("REITs"), REIT-like structures, or real estate operating companies whose businesses and services are related to the real estate industry. The Fund primarily buys common stock but also can invest in preferred stock and convertible securities.<br/><br/>The Fund concentrates its investments in securities of issuers in the real estate industry.<br/><br/>The Fund is classified as non-diversified under the Investment Company Act of 1940, as amended.Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.<ul type="square"><li style="margin-left:-20px"><b>Concentration Risk</b> &#8212;The Fund&#8217;s strategy of concentrating in the real estate industry means that its performance will be closely tied to the performance of a particular market segment. The Fund&#8217;s concentration in these companies may present more risks than if it were broadly diversified over numerous industries and sectors of the economy. A downturn in these companies would have a larger impact on the Fund than on a mutual fund that does not concentrate in such companies. At times, the performance of these companies will lag the performance of other industries or the broader market as a whole. In addition, the real estate industry has historically experienced substantial price volatility.</li></ul> <ul type="square"><li style="margin-left:-20px"><b>Convertible Securities</b> Risk &#8212; The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest or dividends when due, and their market value may change based on changes in the issuer&#8217;s credit rating or the market&#8217;s perception of the issuer&#8217;s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks as apply to the underlying common stock.</li></ul> <ul type="square"><li style="margin-left:-20px"><b>Equity Securities Risk</b> &#8212; Stock markets are volatile. The price of equity securities fluctuates based on changes in a company&#8217;s financial condition and overall market and economic conditions.</li></ul> <ul type="square"><li style="margin-left:-20px"><b>Market Risk and Selection Risk</b> &#8212; Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.</li></ul> <ul type="square"><li style="margin-left:-20px"><b>Non-Diversification Risk</b> &#8212; The Fund is a non-diversified fund. Because the Fund may invest in securities of a smaller number of issuers, it may be more exposed to the risks associated with and developments affecting an individual issuer than a fund that invests more widely.</li></ul> <ul type="square"><li style="margin-left:-20px"><b>Real Estate Related Securities Risk</b> &#8212; The main risk of real estate related securities is that the value of the underlying real estate may go down. Many factors may affect real estate values. These factors include both the general and local economies, vacancy rates, tenant bankruptcies, the ability to re-lease space under expiring leases on attractive terms, the amount of new construction in a particular area, the laws and regulations (including zoning, environmental and tax laws) affecting real estate and the costs of owning, maintaining and improving real estate. The availability of mortgage financing and changes in interest rates also affect real estate values. If the Fund&#8217;s real estate related investments own real estate assets which are concentrated in one geographic area or in one property type, the Fund will be particularly subject to the risks associated with that area or property type. Many issuers of real estate related securities are highly leveraged, which increases the risk to holders of such securities. The value of the securities the Fund buys will not necessarily track the value of the underlying investments of the issuers of such securities.</li></ul> <ul type="square"><li style="margin-left:-20px"><b>REIT Investment Risk</b> &#8212; Investments in REITs involve unique risks. REITs may have limited financial resources, may trade less frequently and in limited volume, may engage in dilutive offerings of securities and may be more volatile than other securities. REIT issuers are also subject to the possibilities of failing to qualify for tax free pass-through of income and failing to maintain their exemptions from investment company registration.</li></ul> <ul type="square"><li style="margin-left:-20px"><b>Small and Mid-Capitalization Company Risk</b> &#8212; Companies with small or mid-size market capitalizations will normally have more limited product lines, markets and financial resources and will be dependent upon a more limited management group than larger capitalized companies. In addition, it is more difficult to get information on smaller companies, which tend to be less well known, have shorter operating histories, do not have significant ownership by large investors and are followed by relatively few securities analysts.</li></ul>Because the Fund does not have a full calendar year of operations, it does not have performance information an investor would find useful in evaluating the risks of investing in the Fund. The Fund&#8217;s primary benchmark is the FTSE EPRA/NAREIT United States Index.0.05250000.0100.00750.00750.00750.00250.0100.03440.03520.03320.04440.05270.0407-0.0314-0.0322-0.03020.0130.02050.0105650308107152812909612081290You would pay the following expenses if you did not redeem your shares:You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in the fund complex advised by BlackRock Advisors, LLC (&#8220;BlackRock&#8221;) and its affiliates.25000Other Expenses have been restated to reflect current fees.A contingent deferred sales charge ("CDSC") of 1.00% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more.The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Fund's most recent annual report, which does not include the restatement of Other Expenses to reflect current fees.0.25June 1, 2014<div style="display:none">~ http://www.blackrock.com/role/ScheduleExpenseExampleNoRedemptionTransposedBlackRockRealEstateSecuritiesFund column period compact * ~</div>
You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.<ul type="square"><li style="margin-left:-20px"><b>Non-Diversification Risk</b> &#8212; The Fund is a non-diversified fund. Because the Fund may invest in securities of a smaller number of issuers, it may be more exposed to the risks associated with and developments affecting an individual issuer than a fund that invests more widely.</li></ul>Because the Fund does not have a full calendar year of operations, it does not have performance information an investor would find useful in evaluating the risks of investing in the Fund.The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Fund's most recent annual report, which does not include the restatement of Other Expenses to reflect current fees.Other Expenses have been restated to reflect current fees.There is no CDSC on Investor C Shares after one year.A contingent deferred sales charge ("CDSC") of 1.00% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more.As described in the "Management of the Fund" section of the Fund's prospectus on pages 28-32, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 1.30% of average daily net assets (for Investor A Shares), 2.05% of average daily net assets (for Investor C Shares) and 1.05% of average daily net assets (for Institutional Shares) until June 1, 2014. The Fund may have to repay some of these waivers and/or reimbursements to BlackRock in the following two years. The agreement may be terminated upon 90 days' notice by a majority of the non-interested trustees of the Trust or by a vote of a majority of the outstanding voting securities of the Fund.